$\"\"$

\

The premutation is $\"\"$

\

The permutation formula is $\"\"$ .

\

$\"\"$ (Apply permutation formula)

\

$\"\"$ (Subtract denominator: $\"\"$ ) $\"\"$

\

$\"\"$ (Expand factorials)

\

$\"\"$

\

$\"\"$ (Cancel common terms)

\

$\"\"$ (Multiply: $\"\"$ ) $\"\"$

\

The number of permutations are 720.

\